Shrinkable tubular fabric

ABSTRACT

A woven tubular fabric which is formed of a set of warp yarns extending longitudinally thereof and a filling yarn interwoven with the warp yarns and extending circularly around the tubular fabric. The filling yarn is heat shrinkable while the set of warp yarns is non-shrinkable so that the woven tubular fabric will shrink in a radial direction upon the application of heat, while the longitudinal dimension remains unchanged.

[ 51 June 13, 1972 United States Patent Woodall, Jr. et al.

....l39/387 UX [54] SHRINKABLE TUBULAR FABRIC 3,242,554 3/1966Raymond....................

3,020,935 2/1962 Balis..........

[72] Inventors: Hubert C. Woodall, Jr., Winston Salem; 910, 91 1/1909Horace L. Freeman, Burlington; Noah C- 2,474,375 6/ 1949 Shearer etGoodman, Winston Salem, all of NC. 2,523,637 9/1950 Stanfield et al.[73] Assignee: Carolina Narrow Fabric Company, Win- 3457962 11/1965Salem NC 1,747,715 2/1930 Hooper... [22] Filed; June 1, 1970 173,6152/1876 Gillespie................................ [21] Appl. No.: 41,997

Primary Examiner-James Kee Chi Attorney-Parrott, Bell, Seltzer, Park &Gibson Related US. Application Data [63] Continuation-impart of Ser. No.502,028, Oct. 22,

ABSTRACT 1 Claim, 4 Drawing Figures References Cited UNITED STATESPATENTS 3,096,560 7/1963Liebig........................................28/72 hmnm iiiee e g.

i T n I a l. J. 5

SHRINKABLE TUBULAR FABRIC This application is a continuation-in-part ofapplication Ser. No. 502,028, filed Oct. 22, 1965 by the same inventors,now abandoned.

The present invention relates to an improved tubular fabric. Moreparticularly, the invention relates to a tubular woven fabric which maybe positioned about an elongated article and radially shrunk by theapplication of heat into a closely conforming relationship with theelongated article, while maintaining the longitudinal dimension of thefabric.

The tubular fabric of the present invention finds utility in a largenumber of applications. For example, the fabric may be utilized as aprotective or insulating covering for an elongated article such as apipe or wire, or it may be utilized as a component in a laminatedarticle such as a glass fishing rod, plastic pipe or the like. Inaddition, the fabric may be used to form a relatively rigid hollowtubular article having independent uses.

It has previously been proposed to employ shrinkable yarns in a woventubular fabric wherein shrinkage occurs in all directions (i.e., bothlongitudinally and radially) such that the tubular fabric may assume thecontours of a mating irregularly shaped elongated article. However,shrinkage in all directions makes it difficult to insure that theresulting longitudinal length of a pre-cut tubular fabric will conformto that of the mating article since the fabric is unconstrained in thelongitudinal direction and the degree of shrinkage is thereforedifficult to control. Thus it is not possible to sell the fabric inprecut standard lengths. In addition, shrinkage in all directionsrequires that a relatively large amount of the tubular fabric beutilized to cover a given article, and thus the cost of the tubularfabric is relatively high.

Accordingly, it is an object of the present invention to provide atubular fabric capable of shrinkage in a radial direction whilemaintaining substantially the same longitudinal dimen- 81011.

It is a further object of this invention to provide a tubular fabricwhich may be easily positioned about an elongated article and radiallyshrunk into closely conforming relationship to protect or insulate thearticle.

It is another object of this invention to provide a versatile tubularfabric which may be employed as a covering, a tubing, or as a componentin the construction of numerous elongated articles.

These and other objects and advantages of the present invention areachieved in the embodiment illustrated herein by the provision of atubular woven fabric comprising a set of non-shrinkable warp yarnsextending longitudinally of the fabric and heat-shrinkable filling yarnextending circularly about the fabric. The fabric is adapted to bepositioned over an elongated article, and upon the application of heatwill radially shrink into a closely conforming relationship whilemaintaining its longitudinal dimension substantially unchanged.

Some of the objects of the invention having been stated, other objectswill appear as the description proceeds, when taken in connection withthe accompanying drawings, in which FIG. 1 is an enlarged sideelevational view of a tubular fabric embodying the features of thepresent invention;

FIG. 2 is a sectional view taken substantially along the lines 22 ofFIG. ll;

FIG. 3 is a side elevational view illustrating the tubular fabric ofFIG. 1 after it has been shrunk about an elongated article, such as amandrel; and

FIG. 4 is a sectional view taken substantially along the lines 44 ofFIG. 3.

Referring to the drawings, a tubular woven fabric is illustratedgenerally at in FIGS. 1 and 2, and comprises a set of non-shrinkablewarp yarns 12 extending longitudinally and substantially parallel to theaxis of the fabric, and heat shrinkable filling yarn 14 extendingcircularly about the fabric and at substantially right angles to thewarp yarns 12.

In FIGS. 3 and 4, a tubular fabric 10' is illustrated whichrepresents'the fabric 10 after it has been subjected to sufi'lcient heatto shrink the filling yarn and thereby reduce its diameter to that of anelongated article on which it has been placed, such as a mandrel,indicated in dotted lines at 16. As will be apparent from the drawings,the longitudinal dimension A of the fabric 10' has not substantiallychanged from the corresponding dimension A of the fabric 10, while thediameter B thereof has been substantially reduced from the diameter B ofthe fabric 10.

The particular number of warp of filling yarns employed in a particularfabric will depend on the desired end use. Thus while a singleshrinkable filling yarn has been shown in the drawings, it will berecognized that a plurality of similar filling yarns could be employedin the fabric. In addition, it has been found that an increase in thenumber of warp yarns for a given diameter will reduce the amount ofshrinkage of the filling yarn. Thus, if a large amount of shrinkage isintended, a relatively small number of warp yarns should be employed.

The non-shrinkable warp yarns 12 may consist of any material that willprovide the insulating, chemical, or mechanical properties required forthe desired end use, and which do not appreciably shrink when subjectedto heat, water, or other chemical action. Typical of such fabricmaterials are glass, asbestos, ceramic, metal wire, and the like.

The filling yarn 14 preferably comprises a heat shrinkable polymericmaterial. Examples of such materials are polyesters, such aspolyethylene terephthalate, acrylics such as polyacrylonitrile, nylon,and polyolefins such as polypropylene and polyethylene. Nylon is asynthetic linear polymer produced by the reaction of .hexamethylenediamine with adipic acid, the molecule being; entirely adiphatic andbased on the formation of polyamides. The various polymeric materialsexhibit a wide range of shrinkages in response to heat, and theparticular one chosen should depend on the temperature at whichshrinkage should take place, the desired percentage of shrinkage of thetube, and the required strength of the finished product. As typicalexamples of properties of these materials, polyester fibers shrinkapproximately 15-17 percent at 300 F., acrylic fibers shrinkapproximately 10-l5 percent at 212 F., and polypropylene shrinks up toapproximately 28 percent at 275 F.

In one embodiment of the present invention, the tubular fabric isutilized as a closely conforming protective or insulating covering foran elongated article such as a pipe, shaft, or wire. Coverings arecommonly applied to the outer surface of such articles to provideelectrical, chemical, or mechanical insulation or protection, and thetubular fabric of the present invention is ideally suited for such usessince it can be easily applied to the article and will result in aclosely conforming, neat appearance. Also, the particular compositionsof the fabric may be selected to include materials which contribute tothe desired properties of the covering; for example, glass warp yarnscould be utilized where a fire retardant covering is desirable.

To provide a substantially rigid tubular insulator or covering memberfor an elongated article such. as an electrical component, the tubularfabric may be impregnated with a heat settable resin, such as apolyester or epoxy resin. The fabric is then placed loosely over theobject to be covered, and heat is applied to shrink the filling yarnsand cure or set the resin. Al tematively, a two step shrinking proceduremay be employed wherein the resin impregnated fabric is first placedover a mandrel which is slightly larger in diameter than the diameter onwhich the tubular fabric is to be ultimately placed. Heat is thenapplied to shrink the filling yarns and partially cure or set the resinto produce a tubular fabric which is sufficiently rigid to retain theshape of the mandrel. In this condition, it is adapted for shipping incommerce as a preformed tubular cover or insulator of a diameterslightly greater than the diameter of the article on which the tubularfabric is to be placed. The user then places it over the article such asa wire or pipe which is ultimately to be covered and the filling yarnshrunk a second time by the application of heat to form a tight fit overthe article. Further details of the process employing a resinimpregnated tubular fabric of this type may be obtained by reference tothe US. Pat. to Wareham, No. 3,466,210.

The tubular fabric of this invention may also be utilized to form ahollow tubular article having independent uses. For example, if the warpyarns are fiber glass and the filling yarns are a heat shrinkablepolymer, the fabric may be placed over a mandrel and, in a singleheating operation the polymeric yarn shrunk to form a relatively rigidpipe-like article. Of course, the fabric could be impregnated with aheat settable resin or a suitable coating could be subsequently appliedto the shrunken fabric to increase the rigidity of the resultingarticle. Such a fiber glass pipe may have many independent uses andapplications, other than a covering for an elongated article.

The present invention may also be employed as a component in theconstruction of numerous elongated articles. For instance, the fabriccould be filled with a lightweight material such as polystyrene foam andfiien subjected to a heating operation to shrink the filling yarns andthereby form a lightweight waterproof object which may serve as a waterfloat. Further, the fabric may be shrunk about a bundle of fiber glassrods to form an elongated circular article such as a fiber glass fishingrod. Still further, the tubular fabric may serve as a strengtheningcomponent in a laminated elongated article such as a fiber glasspole-vaulting pole. In this latter case, the fact that the fabric of theinvention will shrink into a closely conforming smooth covering isimportant, since the outer surface of the pole should be free fromirregularities.

In still another embodiment of the present invention, the non-shrinkablewarp yarns may be thin or fine metallic electrical conducting wires,such as silver, copper or aluminum. This embodiment would beparticularly advantageous in an apparatus where it is necessary to run avery large number of electrical wires along the outer surface of anelongated member such as a shaft. In addition, non-metallic orinsulating yarns could be alternated with the metallic wires in the warpso that the metallic wires are insulated from each other.

Typical applications of the tubular fabric have been discussed above. Itshould be evident however, that the fabric has an almost infinite numberof potential uses. Also, the fabric may be made of any desired length ordiameter depending on the desired end use. In addition, it will beevident that multiple layers of the tubular fabric could be sequentiallyapplied over the elongated article to produce a covering or tubulararticle of substantial thickness.

In the drawings and specification there has been set forth a preferredembodiment of the invention, and although specific terms are employed,they are used in a generic and descriptive sense only and not forpurposes of limitation.

What is claimed is:

1. A tubular woven fabric comprising a set of non-shrinkable warp yarnsformed from material selected from the group consisting of glass,asbestos, ceramic and metal, said warp yarns extending longitudinally ofthe tubular fabric, and heat shrinkable polymeric filling yarn extendingcircularly around the tubular fabric and substantially at right anglesto the warp yarns, whereby the corresponding circular dimension of thetubular fabric may be reduced by the application of heat to the fabricwhile the longitudinal dimension remains substantially unchanged.

1. A tubular woven fabric comprising a set of non-shrinkable warp yarnsformed from material selected from the group consisting of glass,asbestos, ceramic and metal, said warp yarns extending longitudinally ofthe tubular fabric, and heat shrinkable polymeric filling yarn extendingcircularly around the tubular fabric and substantially at right anglesto the warp yarns, whereby the corresponding circular dimension of thetubular fabric may be reduced by the application of heat to the fabricwhile the longitudinal dimension remains substantially unchanged.